JPH0972452A - Control device for electromagnetic proportional flow control valve - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To reduce an overshoot and a control delay due to a delay in current detection when performing opening control of an electromagnetic proportional flow control valve by current feedback. A target current I for an electromagnetic proportional flow control valve
deviation ΔI between o and actual current Ir is calculated, and this deviation ΔI
In the control device of the electromagnetic proportional flow rate control valve that calculates the duty ratio of the drive pulse current to the electromagnetic proportional flow rate control valve based on the proportional-integral control, the calculation of the integral element in the duty ratio calculation means is set from the present time. It is configured to be executed based on the deviation ΔI between the target current Io before the time and the actual current I at the present time, and the integral element in the duty ratio calculating means is provided only during the lapse of a predetermined time from the start of driving the electromagnetic proportional flow control valve. To lose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control used for controlling the operation of a hydraulic actuator such as a lift cylinder for driving a three-point link mechanism for raising and lowering a working device of an agricultural tractor by using an electromagnetic proportional flow control valve. Regarding the device.

[0002]

2. Description of the Related Art In a control device for an electromagnetic proportional flow control valve described above, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-66801, flow control of an electromagnetic proportional flow control valve driven by a pulse current is performed by current feedback. Is going. In other words, the electromagnetic proportional flow rate control valve is driven by a pulse current of a constant cycle, and the pulse current (duty ratio) of this pulse current is changed to change the average current value for the electromagnetic proportional flow rate control valve, in other words, the electromagnetic proportional flow rate control. While controlling the opening of the valve, the deviation between the target current and the measured actual current for the electromagnetic proportional flow control valve is calculated, and based on the proportional deviation integral control (PI control) from this current deviation, the electromagnetic proportional flow control valve The duty ratio of the drive pulse current is calculated.

In such control by current feedback, since the deviation between the target current and the actual current is large at the time of starting the electromagnetic proportional flow control valve, the integral factor is greatly utilized and the duty ratio is set excessively. There is a possibility that an overshoot may occur before the drive current reaches a stable state, and such an overshoot may cause the actuator to overdrive, resulting in a drive shock. It happened. Therefore, in the above-mentioned conventional example, the integral element in the duty ratio calculation is eliminated only during a predetermined time period from the start of driving the electromagnetic proportional flow control valve, that is, only during the transition period when the deviation between the target current and the actual current is large. The ratio is prevented from being set excessively.

[0004]

The above-mentioned conventional device is effective in suppressing overshoot, but the following control problems have been observed. In other words, in the above control, the actual current is measured and the deviation between the actual current and the actual current is calculated after the actual current is calculated. Becomes larger, and the duty ratio is integrated so that the duty ratio is still slightly larger. As shown in FIG. 6, after the target current increases, the target current increases and decreases slightly at the peak position. There was a tendency for delay to occur overall in the region where the target current decreased as the shoot remained. An object of the present invention is to make it possible to execute the current control immediately after the start of driving and the current control thereafter with little overshoot and delay.

[0005]

The features of the present invention include a deviation calculating means for calculating a deviation between a target current and an actual current for an electromagnetic proportional flow control valve, and a proportional integration control based on the current deviation. A control device for an electromagnetic proportional flow control valve, comprising: a duty ratio calculation means for calculating a duty ratio of a drive pulse current with respect to the proportional flow control valve; Is configured to be executed based on the deviation between the target current and the actual current at the present time, and the gain of the integral element in the duty ratio calculation means is set only during a predetermined time period from the start of driving the electromagnetic proportional flow control valve. The point is that a calculation correction means for changing the value to zero or a value close to this is provided.

[Operation] According to the above configuration, the duty ratio is calculated because the deviation between the target current value and the actual drive current is large during transient control such as when the electromagnetic actuator is driven. In this case, since the term of the integral element, which is effective in a large proportion of the arithmetic expression, is eliminated or almost eliminated and only the term of the proportional element is calculated, it is possible to suppress the occurrence of overshoot in the subsequent current increase as much as possible, Smooth control drive can be performed. Further, after the transient state, since the duty ratio calculation with the effect of the integral element is performed, highly accurate control without residual deviation is executed. In this case, there is a time delay between the output of the target current and the measurement of the actual current.Therefore, in the calculation of the integral element, the duty ratio is calculated from the deviation between the target current before the set time before the current time and the actual current at the current time. By performing the calculation, it is possible to avoid excessive calculation of the current deviation,
As shown in FIG. 5, after the target current has increased, the overshoot at the peak portion that decreases decreases, and
The delay in the region where the target current decreases is small.

[Effect] Therefore, in the automatic control of the feedback system, even when the proportional-integral control in which the occurrence of hunting is small and the residual deviation is small is used, it is possible to perform a transient operation such as when the electromagnetic actuator is started. In such a state, the overshoot phenomenon can be suppressed, and the smooth current rising drive can be performed, so that the drive shock of the driven device can be suppressed. In addition, in the proportional-plus-integral control after the transitional period, it is possible to perform control with excellent responsiveness in which the overshoot and control delay due to the current detection delay are suppressed.

[0008]

1 shows an agricultural tractor to which the present invention is applied. This agricultural tractor is configured by connecting a rotary tiller 3, which is an example of a working device, to a rear part of a tractor main unit 1 via a hydraulically driven three-point link mechanism so as to be able to move up and down. The three-point link mechanism 2 is composed of a single top link 2a and a pair of left and right lower links 2b. The three-point link mechanism 2 includes a pair of left and right lift arms 4 and a left and right lower links 2b that are vertically swingable in the tractor unit 1. It is connected through a lift rod 5 and a rolling cylinder 6, and the lift arm 4 is driven and oscillated by a lift cylinder 7 to elevate and lower the rotary tiller 3, and by expanding and contracting the rolling cylinder 6, the rotary tiller 3 is moved. It is configured so that it can be tilted (rolled) left and right.

FIG. 2 shows a hydraulic system for driving the rolling cylinder 6 and the lift cylinder 7. In this hydraulic system, the pressure oil from the hydraulic pump P driven by the engine E is diverted via the flow priority valve 8.
A rolling control system for supplying a controlled flow of a constant flow rate to the rolling cylinder 6 via the rolling control solenoid valve 9 is constructed, and the surplus flow from the flow priority valve 8 is lifted via the electromagnetic proportional flow control valve V. An elevating control system for supplying to the cylinder 7 is configured.

The electromagnetic proportional flow control valve V includes a rising control valve uV, a rising pilot operation valve up for controlling pilot pressure to the rising control valve uV, and a lowering control valve dV.
And a relief pilot valve dp for controlling the pilot pressure for the lowering control valve dV, and a relief valve rV.
By supplying a current to the solenoid us of the pilot operating valve for raising up and adjusting the current value of this current, the pilot operating valve for raising up changes the pilot pressure in accordance with the current value, and The opening degree of the control valve uV changes in proportion to the pilot pressure, and the flow rate of the pressure oil from the hydraulic pump P can be adjusted and controlled.
When the lift arm 4 is controlled to the descending side, a current is supplied to the solenoid ds of the descending pilot operating valve dp and the current value is adjusted to change the pilot pressure from the pilot operating valve dp. It is configured so that the opening degree of the lowering control valve dV changes and the flow rate of the hydraulic oil flowing out of the lift cylinder 7 can be adjusted and controlled.

As shown in FIG. 3, the current supply control system for each of the solenoids us and ds is provided with a control device 10 having a microcomputer, and serves as a position setter for setting the height of the tiller 3 with respect to the machine body. A first potentiometer PM1, a second potentiometer PM2 for detecting and feeding back the actual height of the tiller 3 with respect to the machine body as a swing angle of the lift arm 4, a third potentiometer PM3 as a tiller, and a rotary tiller. Cover sensor 3a mounted on 3 so that it can swing up and down
A fourth potentiometer PM4 for detecting and feeding back the swing angle of each as the actual plowing depth, and an A / D converter 13 for digitizing the signals of these potentiometers PM1, PM2, PM3, PM4 and inputting them to the controller 10. In addition, the control device 10 includes a power transistor uT that supplies electric power to the solenoids us and ds.
It has an output system for r and dTr, and each solenoid u
In order to obtain the average current value of the pulse currents supplied to s and ds, a resistor 11 is provided in the path through which the current from the solenoids us and ds flows, and the voltage signal obtained by this resistor 11 is applied to the smoothing circuit 12. The A / D converter 13 converts the signal into a digital signal and feeds it back to the control device 10.

Next, the operation of controlling the tilling depth of the tiller 3 will be described with reference to the flowchart of FIG. When the outputs of the third and fourth potentiometers PM3 and PM4 are read, the deviation ΔX of each output is calculated, and when the absolute value of this deviation ΔX is larger than the set value M, the deviation to the lift cylinder 7 is determined based on the deviation ΔX. The drive condition, that is, the opening of the electromagnetic proportional flow rate control valve V, is obtained as the target current Io to be supplied to either the solenoid us or the solenoid ds and the duty ratio Do for obtaining this target current Io (steps 1 to 1). 3). Then, based on the obtained duty ratio Do, the solenoid us of the electromagnetic proportional flow control valve V
Alternatively, a current is supplied to either ds (step 4).

Next, the actual current Ir is read from the voltage value obtained by the resistor 11, and the deviation ΔI between this actual current Ir and the target current Io is calculated (steps 5 and 6) to obtain this current deviation. When ΔI is larger than the dead zone width N, it is determined whether or not the current value Iro before control driving in the solenoid us or ds is zero. If it is not zero, it is determined that normal operation is performed, and The duty ratio D1 for the solenoid us or ds is calculated by proportional-plus-integral control based on the current deviation ΔI (steps 7 and 8), and the current is supplied to the solenoid us or ds by this duty ratio D1 until the current deviation ΔI becomes zero. Yes (Step 9-
11).

Here, in the calculation of the duty ratio D1, the deviation ΔI used for the integration element is set as the deviation between the target current Io before the set time before the present time and the actual current Ir at the present time, thereby delaying the current detection. Is being corrected. As the target current Io before the set time, the average value of the target current Io before and after the set time may be used. For example, in order to obtain the target current Io 25 milliseconds before the present time, the average value of the target current 20 milliseconds before and the target current 30 milliseconds before is used.

When the current value Iro before the control drive in the solenoid us or ds is zero, it is determined that the solenoid us or ds has started to be activated, and the gain b of the integral element is set to zero. Execute duty ratio calculation. That is, the duty ratio D2 is calculated only by the proportional control that does not include the integral element, and the duty ratio D2 is calculated.
The current is supplied by 2 (steps 12 and 13).

When about several tens of milliseconds (for example, 50 milliseconds) have elapsed from the time when the current supply was started at the duty ratio D2, the process returns to step 8 and shifts to the duty ratio calculation operation by the proportional-plus-integral operation (step 14). Then, such control is repeatedly executed until it is reset (step 15).

The deviation calculating means A is constituted by the step 5, the calculation correcting means C is constituted by the steps 12 to 14, and the duty ratio calculating means B is constituted by the steps 8 and 12.

Incidentally, FIG. 5 is a characteristic diagram when current control is performed according to the present invention. As can be seen from the figure, overshoot and delay are less than in the conventional case (see FIG. 6). Current control is possible.

Further, although detailed description is omitted, also in the position control for raising and lowering the tiller 3 to a height corresponding to the set value of the first potentiometer PM1, the integral element in the proportional-plus-integral control is set for the set time at the initial stage of activation. Since the control is performed according to the above characteristic of changing to zero, the tiller 3 can be accurately moved up and down to a desired height without overshoot.

It should be noted that the duty ratio calculation may be executed in a state in which the gain b of the integral element is reduced to a value close to zero during the set time from the start of the activation to reduce the influence of the integral element.

Further, although reference numerals are given in the claims for facilitating the comparison with the drawings, the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a perspective view showing a rear portion of an agricultural tractor.

[Fig. 2] Hydraulic circuit diagram

FIG. 3 is a control block diagram.

FIG. 4 is a control flowchart.

FIG. 5 is a control characteristic diagram by the device of the present invention.

FIG. 6 is a control characteristic diagram of a conventional device.

[Explanation of symbols]

 A deviation calculation means B duty ratio calculation means C calculation correction means V electromagnetic proportional flow control valve Io actual current Ir actual current ΔI deviation

Claims (1)

[Claims] 1. A deviation calculating means (A) for calculating a deviation (ΔI) between a target current (Io) and an actual current (Ir) with respect to an electromagnetic proportional flow control valve (V), and a proportional integral from the current deviation (ΔI). A control device for an electromagnetic proportional flow rate control valve, comprising: a duty ratio calculation means (B) for calculating a duty ratio of a drive pulse current to the electromagnetic proportional flow rate control valve (V) based on control; The calculation of the integral element in the means (B) is executed based on the deviation (ΔI) between the target current (Io) set time before the present time and the actual current (Ir) at the present time, and the electromagnetic proportional flow rate is also provided. Control valve (V)
Is provided with an operation correction means (C) for changing the gain of the integral element in the duty ratio operation means (B) to zero or a value close thereto only during a predetermined time from the start of driving. Control device for electromagnetic proportional flow control valve.